In the current state of the art, optical components are typically manufactured as individual components and subsequently assembled and integrated into functional detecting (focusing) and/or displaying devices. For example, conventional solid-state image detectors which are either charge-coupled devices (CCD) or complementary metal-oxide semiconductor (CMOS) photodiodes are typically manufactured as array structures which comprise a spectrally photosensitive layer assemble below one or more layers patterned in an array of color filters and above the array of color filters resides an array of microlens elements.
One example of conventional color image display is the digital light processor (DLP) system developed by Texas Instruments. In the DLP system, light is projected onto a deformable micro-mirror device (DMD) by a color filtered array of light emitting diodes (LEDs). Under digital control circuitry, the DMD sequentially displays different color segments of an image. Red, green and blue components of an image are displayed when the DMD is illuminated by one of a red, green or blue LED through a corresponding one of a red, green or blue filter. In order to obtain appropriate image brightness and color quality, arrays of LEDs must be focused onto the DMD with the use of corresponding focusing and filtering micro-optical elements. These micro-sized lens and filter elements, which are in the order of tens of microns in thickness and can be as small as 10 microns in diameter, are separately layered onto and aligned with the LEDs.
In the field of fiber-optic communications, appropriate focusing elements are routinely combined with wavelength selective optical filters, wavelength splitters, optical couplers, waveguides and the like. Because wavelength selective elements, optical couplers and the like are typically manufactured as separate parts, assembling and aligning these into high-precision optical components represents a major hurdle.
It is evident therefore, that separately fabricating highly precise optical elements and then aligning with LED, CCD, CMOS or wavelength selective devices is a difficult, costly and time-consuming process. FIG. 1A graphically illustrates an example of a Prior Art process for the formation of a microlens array and the assembly and alignment of said microlens array with a color filter array and an image sensor substrate. The formation of a microlens array is illustrated at 100, in which a planar film of a photoimageable material such as a photoresist is photolithographically patterned such that exposure to actinic radiation and subsequent development of the photoresist forms a two-dimensional array of mesas which can be thermally reflowed (melted) into planoconvex microlenses under surface tension forces. An exploded assembly view is shown in 110, indicating the relative position and alignment of the microlens array elements to an underlying array of red, green, blue color filters and further underlying sensor substrate including an array of image sensors. By electronically amplifying and combining the outputs of the red, green and blue signals detected by the image sensors, color image formation is achieved. One of the problems with the above-describe process is that topographical variations and misalignment caused by the process assembling separate optical components with the semiconductor device result in optically generated cross-talk and/or poor resolution imaging.
In view of the foregoing and other considerations, it would be advantageous to develop improved techniques that enable the integration of different optical components preferably into a single one, thereby overcoming the problems caused by separately fabricating such optical components and subsequently assembling and aligning them.